I’m not familiar with Leviton’s solution, but do they have an option to “Receive Network Updates”?. I had an Aeon Z-Stick as a secondary and when I added a device with SmartThings, I had to request network updates. SmartThings would send the changes over to the Secondary Controller rather quickly.
Also, if you have a 2nd gen hub like mine, then the above might not be possible. Check in the IDE that your HUB has a SUCID of 1. If it is 0, then you will have to wait for SmartThings to fix it before you can do the above.